JPS6364425B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new and simple method for producing percarboxylic acids, which are particularly useful for the selective oxidation of organic compounds. It is known from the literature of Ans et al. (Berichte 4518451912) that hydrogen peroxide reacts with aliphatic carboxylic acids to form percarboxylic acids by an equilibrium reaction that can be described as follows: In view of the instability of peroxyacids, this reaction is generally carried out at low temperatures. Under these conditions, equilibrium is reached only after a reaction period of several hours, a period which is inhospitable to industrial processing. It is thus necessary to rely on catalysts. Only one type of catalyst has hitherto been proposed, namely strong mineral acids such as sulfuric acid, methanesulfonic acid, arylsulfonic acids, phosphoric acid, acid phosphate esters, trifluoroacetic acid and also acid cationic resins such as "Dowex". 50'' or ``Amberlite IR-120'' have been proposed. This contact treatment formed the basis of numerous studies (D. Swern, ``Organic peroxides'').
Peroxides), Wiley Interscience, 1970, 1 volume,
313-369 and 428-439). It is clear from these studies that the first step of the reaction corresponds to the protonation of the acid group to form an oxonium structure, which reacts with H ₂ O ₂ according to the following formula and after dehydration. has the ability to generate percarboxylic acids; Hydrogen peroxide is most often used in the form of commercially available aqueous solutions containing 30-70% water. Furthermore, the reaction produces water. As a result, equilibrium is well reached before all of the hydrogen peroxide is converted. Under these conditions, the reaction product is effectively a mixture of acid, hydrogen peroxide, peracid, water, and strong acid. Use of this mixture as an oxidation tool in organic chemistry thus gives rise to very mediocre yields. To overcome this drawback, it has been proposed to carry out the reaction in the presence of a very large excess of carboxylic acid to shift the equilibrium reaction to the right. That is, by using 10 moles of acetic acid per mole of hydrogen peroxide, a degree of conversion of 90% of the hydrogen peroxide to peracetic acid can be achieved. Using such an excess amount will only result in a very dilute solution of peracid and will cause losses in yield due to side reactions, not to mention the problems of subsequent separation of the reaction products. many. Therefore, as in US Pat. Nos. 2,877,266 and 2,814,641 and Belgian Patent No. 5,59665, azeotropes in which the reaction is carried out with a very slight excess of carboxylic acid, but in the presence of a strong mineral acid catalyst and with the removal of water; It was proposed to carry out the reaction in the presence of an entraining agent, thus shifting the equilibrium reaction () to the right. In practice, this practice is excellent in terms of yield of percarboxylic acid with respect to the hydrogen peroxide used. Compared to conventional techniques, this technique is expected to provide good yields for organic chemistry oxidation reactions. However, this is rarely the case and the yield can be even more mediocre. This is because strong acid catalysts very often cause side reactions. For example, it is well known that in reactions involving epoxidation of olefins with peracids, the epoxides formed are easily cleaved and converted to monoesters or diesters under the action of strong acid catalysts. On the other hand, French Patent No. 2,038,575 describes the use of organic compounds as oxygen acceptors or electron donors with oxygen vectors obtained from inorganic materials such as metalloids such as selenium by oxidation with peroxides such as hydrogen peroxide. The cyclic and indirect oxidation of This oxidation is preferably carried out in xylene, during which the water resulting from the reaction and from the reactants is continuously entrained azeotropically. This method is particularly suitable for oxidizing 2-methylpyridine, paraldehyde, acetone, acetophenone, and hydroquinone, but requires three consecutive steps: (a) converting the metalloid to the metalloid oxide with hydrogen peroxide; formation of (b)
Oxidation of organic compounds by metalloid oxides, during which the metalloid oxides are reduced and the metalloids are precipitated, (c)
Recirculation of precipitated metalloids. That is, such methods are more difficult to implement and therefore more expensive. Although strong acids can be advantageously neutralized, it is true that the corresponding salts are then generally insoluble in the medium and give rise to considerable separation problems from an application point of view. in some cases,
It is even as good a catalyst for side reactions as strong acids themselves. It is for this reason that two-step processes for producing organic solutions of percarboxylic acids have recently been proposed, such as in French Patents Nos. 2,359,132 and 2,300,085, in which 10-45% sulfuric acid and 20-35% The method consists in reacting an aqueous solution containing hydrogen peroxide with propionic acid and then extracting the perpropionic acid using a solvent such as benzene or dichloropropane.
The aqueous phase must be concentrated to remove the water provided by H ₂ O ₂ and the reaction. The organic phase is washed to remove H ₂ SO ₄ and then dried, for example by azeotropic distillation. In practice, this solution makes it possible to obtain sulfuric acid-free organic solutions of perpropionic anhydride. However, the technique is complex and therefore expensive to implement. Continuing research in the field of using hydrogen peroxide in organic chemistry, the present inventors have now discovered that in the presence of a novel catalyst made of a metalloid oxide, water and water provided by an aqueous solution of hydrogen peroxide. The same result can be achieved by reacting the carboxylic acid with hydrogen peroxide in the presence of an azeotrope entrainer such that the water resulting from the reaction is continuously removed from the reaction medium; That is, an anhydrous organic solution of percarboxylic acid containing no traces of strong mineral acid can be obtained. Metalloid oxides falling within the scope of the invention include selenium,
It is an oxide of arsenic, antimony, and boron.
Examples include, but are not limited to, the following oxides: SeO ₂ , As ₂ O ₃ , As ₂ O ₅ , Sb ₂ O _{5
and B2O3} . Carboxylic acids in connection with the present invention are water-soluble aliphatic carboxylic acids, namely formic acid, acetic acid, propionic acid and butyric acid. The azeotrope entrainer may advantageously be selected from solvents having a boiling point below 100° C. and forming a heterogeneous azeotrope with water. Examples of solvents that may be mentioned include, but are not limited to; chlorinated solvents such as chloroform, carbon tetrachloride, methylene chloride, 1,
2-dichloroethane and dichloropropane, hydrocarbon solvents such as cyclohexane, benzene and toluene, and esters such as the methyl esters of formic acid, acetic acid, propionic acid, butyric acid and isobutyric acid,
Ethyl ester, propyl ester, isopropyl ester and n-butyl ester. Hydrogen peroxide within the scope of the invention can be used in anhydrous form or in the form of a commercially available aqueous solution with a concentration of 30 to 70% by weight. The process of the invention thus consists in contacting the carboxylic acid, the azeotrope entrainer, the catalyst and hydrogen peroxide, with water being continuously removed from the reaction medium by azeotropic distillation. The temperature to carry out the reaction is 40℃~100℃, 40~70℃
Preferably it is .degree. Depending on the temperature chosen and the reaction system used, water removal can be carried out at atmospheric pressure or under reduced pressure. Thus the pressures are 20mmHg and 760mmHg
It can vary between. The reaction time depends on the type of catalyst, the type of carboxylic acid, the type of azeotrope entrainer and the temperature chosen. Reaction times can range from a few minutes to several hours.
Although the reactants may be used in equimolar amounts, a molar excess or molar deficit of one or more of the reactants may be used. As a scale, 0.1 to 10 per mole of hydrogen peroxide
Although moles of carboxylic acid may be used, it is preferred to use 1 to 5 moles of carboxylic acid. The catalyst is used in a ratio of 0.001 to 0.1 mole of metalloid oxide per mole of hydrogen peroxide. however,
A molar ratio of 0.001 to 0.01 mole per mole of hydrogen peroxide used is preferred. The amount of azeotrope entrainer solvent is 50-75% of the reaction mixture.
% by weight, so that the boiling point of the mixture can be adjusted as desired and water can be removed effectively. The reactants can be used in their normal commercially available forms. In particular, hydrogen peroxide can be used in the form of a commercially available aqueous solution with a concentration of 30 to 70% by weight. It may be advantageous to add to the reaction medium compounds for stabilizing hydrogen peroxide, such as polyphosphates, derivatives of ethylenediaminetetraacetic acid (EDTA), and the like. The solutions of percarboxylic acids thus obtained can then be used in further operations to carry out the oxidation of a large number of organic compounds such as olefins, ketones, amines, aromatics, sulfur derivatives and the like. However, it is not always necessary to resort to this method, and it is sometimes advantageous to be able to carry out the two operations simultaneously, namely the synthesis of the peracid and the direct consumption of the peracid by the molecule to be oxidized. . This constitutes a modification of the method of the invention. That is, if the organic compound that it is desired to oxidize with a percarboxylic acid forms a heterogeneous azeotrope with water, this can be used as an entrainer for the azeotrope, and the percarboxylic acid is formed in the same step. As the temperature increases, it can be reacted with percarboxylic acid. Examples that may be mentioned are the epoxidation of cyclohexene or allyl chloride with peracetic acid or perpropionic acid. This method is particularly simple to carry out and is particularly safe. This is because the process avoids the accumulation of peracid in the reaction medium. Within the scope of this variant, it is of course possible to carry out the reaction in the presence of an azeotrope entrainer solvent, provided that the compound to be oxidized does not form a heterogeneous azeotrope with water. The present invention will be illustrated by the following examples, but the present invention is not limited thereto. Examples 1 to 9 50 g of propionic acid, 70 g of azeotrope entrainer solvent and 0.2 g of catalyst were added to a 250 cm ³ column equipped with a 5-plate Oldershaw distillation column equipped with a reflux condenser. Charge the reactor. The mixture is heated to reflux temperature and then 0.1 mol of hydrogen peroxide in the form of a 70% strength by weight aqueous solution is gradually introduced. The reflux condenser is designed in such a way that only the condensed organic phase is refluxed to the distillation column, while the decanted aqueous phase is continuously drawn off. The reaction conditions and results are recorded in the following table. Example 10 125 g of propionic acid, 175 g of 1,2-dichloroethane, 0.5 g of boron oxide B ₂ O ₃ and 0.1 g of disodium phosphate were placed in a reflux condenser of the same type as previously described. A 500 cm ³ reactor equipped with a 10-plate Olderschill distillation column is charged. The mixture is heated to reflux temperature under a pressure of 150 mm Hg. The temperature of the reaction medium is 50°C. Gradually add 0.3 mol of hydrogen peroxide in the form of an aqueous solution with a concentration of 70% by weight. Water was continuously removed by azeotropic distillation during a reaction period of 2 hours, after which 0.24 mol of perpropionic acid and 0.027 mol of hydrogen peroxide were determined in the reaction medium, whereas the distilled aqueous phase contained 0.032 mol of hydrogen peroxide. Contains moles of hydrogen peroxide. Example 11 The same experiment as Example 7 is repeated, but acetic acid is used instead of propionic acid. After a 60 minute reaction period,
0.07 mol peracetic acid and 0.026 mol hydrogen peroxide were measured in the reaction medium, while 0.004 mol hydrogen peroxide was passed into the aqueous phase of the distillate. Example 12 To 120 g of perpropionic acid solution prepared according to Example 10 and containing 0.09 mol of perpropionic acid, 8.2 g of cyclohexene are added at room temperature. After a reaction period of 1 hour, 0.08 mol of cyclohexene epoxide is determined by gas phase chromatography.

[Table] Example 13 50g of propionic acid, 50g of allyl chloride and 0.1
g of arsenic oxide As ₂ O ₅ are charged into a reactor as described in Example 1. The mixture is heated to reflux temperature and the temperature of the reaction medium stabilizes at 64°C. 0.053 mol of hydrogen peroxide in the form of a 70% strength aqueous solution is added within 15 minutes, and the water provided by H ₂ O ₂ and the water formed during the reaction are continuously removed. After a reaction period of 1 hour, 0.034 mol of epichlorohydrin and
0.008 mol perpropionic acid and 0.006 mol hydrogen peroxide are measured in the reaction medium, but the distillate is
Contains 0.004 moles of hydrogen peroxide. Example 14 After passing through a mixer, a perpropionic acid solution prepared according to Example 10 and containing 6.6% perpropionic acid and 0.25% hydrogen peroxide was added.
100g/hour and 21g/hour of propylene, 15m
A tubular reactor having a length of 2 mm and a diameter of 2 mm is charged sequentially and simultaneously. Maintain reactor temperature at 50°C. The pressure in the reactor is 8 bar. When the reactor is left alone, the reaction mixture is continuously depressurized.
The gas phase is washed with water in a washing tower to recover entrained propylene oxide. Cool the liquid phase. Analysis of the reaction products shows that 0.011 moles of perpropionic acid leave the reactor per hour;
g/h of propion oxide is produced.

Claims (1)

[Claims] 1. Consisting of reacting hydrogen peroxide with a water-miscible saturated aliphatic carboxylic acid in a homogeneous liquid phase at a temperature of 40 to 100 °C in the presence of a catalyst and a solvent, Process for the production of percarboxylic acids, wherein the solvent is used in an amount of 50 to 75% by weight of the reaction mixture and can be continuously removed by azeotropic distillation with the water resulting from hydrogen peroxide and the water formed during the reaction. , wherein the catalyst is a metalloid oxide selected from the group consisting of boron oxide, arsenic oxide, selenium oxide and antimony oxide, and is used in a ratio of 0.001 to 0.1 mole per mole of hydrogen peroxide. A method for producing percarboxylic acid. 2. The method according to claim 1, in which a chlorinated solvent is used as an entraining agent for the azeotrope. 3. The method according to claim 1 or 2, in which benzene is used as an entraining agent for the azeotrope. 4. The method according to any one of claims 1 to 3, wherein the water-miscible aliphatic carboxylic acid is acetic acid. 5. The method according to any one of claims 1 to 3, wherein the water-miscible aliphatic carboxylic acid is propionic acid. 6. Any one of claims 1 to 5, wherein the azeotrope entrainer used is an organic compound that can be oxidized with percarboxylic acid aliphatics as the percarboxylic acid is formed in the reaction medium. The method described in. 7. The method according to claim 6, wherein the entraining agent for the azeotrope is an olefin. 8. The method according to claim 7, wherein the entraining agent for the azeotrope is cyclohexene. 9. The method according to claim 7, wherein the azeotrope entraining agent is allyl chloride.